Heating- unit with embedded tubular element



1965 w. H. NORTON 3,201,568

HEATING UNIT WITH EMBEDDED TUBULAR ELEMENT Filed NOV. 29, 1962 2Sheets-Sheet 1 /7 Fig.6

M) Eq Z E INVENTOR 48 /1 /am f7. War/on deceased I Z rm .n/arfan I Byby59d M/lsf/zzr r/fx TORNEYS Aug. 17, 1965 w. H. NORTON HEATING UNIT WITHEMBEDDED TUBULAR ELEMENT Filed Nov. 29, 1962 2 Sheets-Sheet 2 UnitedStates Patent 3,201,568 HEATING UNIT WITH EMBEDDED TUBULAR ELEMENTWilliam H. Norton, deceased, late of Mundelein, Ill, by

Lynn W. Norton, administratrix, Mundelein, Ill., assignor to ThermelIncorporated, Franklin Park, Ill., a corporation of Delaware Filed Nov.29, 1962, Ser. No. 241,069 7 Claims. (Cl. 219-538) The present inventionrelates to a heating device, and more particularly to an improvedretainer or mount for housing and enclosing a tubular type of electricheating element, and to the method of making the structure.

In a tubular type of electrical heating element a resistance wire isencased within and insulated from an outer protective enclosing tube ofmetal. Such electrical heating units have enjoyed popularity because oftheir cornparative high efficiency and speed of operation. The units areemployed for many purposes where heat is to be transmitted to a surfaceor to an area and the units are employed industrially or in appliancesof various types. It is customary for the distribution of heat to encaseor mount the tubular heating elements in a metal enclosure. This hasbeen done in various ways such as by providing channels in a metal plateor bar and laying the tubular element in the channels. Metal plates orbars have also been cast around the tubular elements by supporting theelements in a mold and pouring molten metal into the mold. An essentialproperty of a metal retainer for the tubular element is that it be ingood heat conductive relationship with the outer surface of the tubularelement. It is also desirable that the retainer or housing for the tubebe simple and inexpensive to manufacture.

It is accordingly an important object of the present in vention toprovide an improved electric heater wherein a tubular heating element isencased or mounted in a plate or a bar by a simplified and improvedinexpensive method of manufacture.

A further object of the invention is to provide an improved electricheater wherein a tubular element is encased in a metal bar and whereinthe bar is in intimate firm heat conductive relationship with the outersurface of the tube.

A further object of the invention is to provide an improved method ofmanufacture for an electrical heater wherein it is unnecessary to castthe metal of the retainer around the tubular element and disadvantagesof structures heretofore provided are eliminated.

Another object of the invention is to provide an improved structure andmethod of manufacture thereof for an electrical heater particularly welladapted to enclose a U-shaped tubular heating element in a heavy bar orplate.

Other objects, advantages and features will become more fully apparentwith the teaching of the principles of the invention in connection withthe disclosure of the preferred embodiments in the specification andclaims in conjunction with the accompanying drawings, in which:

FIGURE 1 is a perspective view of a heater, with portions shown indisassembled position, constructed in accordance with the principles ofthe present invention;

FIGURE 2 is an end elevational view with parts removed, takensubstantially along line lIIl of FIGURE FIGURE 3 is a vertical sectionalview with parts re moved taken substantially along line III-III of FIG-URE 1;

FIGURE 4 is a fragmentary side elevational view showing a relationshipbetween two electric heaters;

FIGURE 5 is a fragmentary sectional view taken substantially along lineVV of FIGURE 1;

FIGURE 6 is a vertical sectional view taken through another form ofelectric heater constructed in accordance with the principles of thepresent invention;

FIGURE 7 is a fragmentary sectional view taken substantially along lineVIIVII of FIGURE 6;

FIGURE 8 is a vertical sectional view shown in somewhat schematic formand illustrating a step in the method of making the heater of FIGURE 6;

FIGURE 9 is a fragmentary perspective view illustrating another form ofheater;

FIGURE 10 is a horizontal sectional view taken substantially along lineXX of FIGURE 9 with the heating elements omitted;

FZGURE 11 is a vertical sectional view taken through another form ofheater;

FIGURE 12 is a top plan view of the lower section of the structure ofFIGURE 11; and

FIGURE 13 is a vertical sectional view illustrating somewhatschematically a step in the method of making the heater of FIGURE 11.

On the drawings:

FTGURES 1 through 5 illustrate an electrical heater including a bar orplate 15 with a tubular sleeve type heating element 18 housed orenclosed therein. The heating element 13 has an outer sleeve formed ofmetal such as stainless steel, and within the element is an elongatedresistance wire which may be wound into a helix and embedded in aninsulating material such as magnesia. A heating element of this type isdescribed in the William H. Norton US. Patent 2,875,312.

The heating element 18 is bent with parallel linear sides 19 and 20joined by a U-shaped base 21. The bar 15 has linearly extending parallelholes 16 and 17 therethrough for receiving the sides 19 and 26 of theheating element 13.

At one end, the upper half of the bar is cut away as illustrated at 22,down past the axial center of the holes 16 and 17 so that the ends ofthe tubular elements may be bent upwardly to be attached to terminalsfor con necting to an electrical circuit.

The other end is provided with an insertion slot 24 which extendslaterally across the bar 15 and is open at the end of the bar. The slothas a height substantially equal to the diameter of the holes 16 and 17and is uniform in depth with planar upper and lower surfaces so as to bein firm surface-to-surface engagement with an end plug 25 which isinserted into the slot 24 after assem- The slot 24, FIGURE 5, isprovided with a concave surface 33, which is preferably concave in avertical plane and in a horizontal plane so as to conform substantiallyexactly to the curvature of the end 21 of the heating element, so thatthe element will be in firm surface engagement for heat transmission tothe metal of the bar 15.

Similarly, the plug 25 has a surface 26 which is concave in vertical andhorizontal planes to conform to the outer surface of the base 21 of theheating element so that the plug will be in firm surface heat conductiveengagement with the element 18.

The bar 15 is made of metal, preferably of aluminum, and can be madeinexpensively and rapidly by an extrusion process. This permitsextrusion of a long bar, which can be cut into sections, and one end cutaway as illustrated at 22. and the other end formed with slots 24, andthis can be readily accomplished by a milling process. The sections ofthe bar may be provided with mounting means such as illustrated by theholes 23. The U-shaped tubular heating elements 18 are inserted into theholes 16 and 17, and the lead ends are bent upwardly. The plug 25 isthen forced into place and secured there such as by spot welding orother suitable securing means.

FIGURE 4 illustrates two adjacent plates 27 and 2% in abuttingrelationship with their fiat surfaced ends 31 and 32 in heat transferengagement. The end plugs 29 and have end surfaces to conform with theend surfaces of the plates so as also to be in surface-to-surfaceengagement. The length of the plug, and of the slotted ends of the barswhich receive the plugs, is such that it is substantially equal toone-half of the distance between holes 16 and I7, and thus the length ofheating element provided in the U-shaped base 21 will be the same perunit of length for the end of the bar as for the 'body portion of thebar. In other words, uniform heating will occur throughout the length ofthe bar to the very end, and when bars are placed in abuttingrelationship as illustrated in FIGURE 4 a uniform temperature can bemaintained therealong.

FIGURE 6 illustrates a bar or plate 36 with longitudinally extendingholes 37 and 33 therethrough. A tubular sheet type heating element 49 isprovided with ends inserted into the holes, and one side of the elementis omitted from the hole 38 for purposes of illustration. It willhowever be understood that the principles of the invention may beemployed in various environments without employing a specific U-shapedtubular element.

In accordance with the arrangement of FIGURE 6, a recess or slot 41 isprovided extending radially from the hole 37. While only one recess maybe employed, in a preferred arrangement diametrically opposed recesses41 and 4-2 are provided for the hole 37, and recesses or slots 43 and 4dare provided for the hole 33. These recesses extend laterally'orhorizontally for ease in collapsing the recesses as will be described inconnection with FIG- URE 8.

The end of the bar 36 may have the end cut away at 39, as illustrated inFIGURE 7, and this will have the appearance and construction of thearrangement shown at 22 in FIGURE 1. The other end will have a slot andplug in the same manner as the structure of FIGURE 1.

In manufacture and assembly of the unit of FIGURE 6, the bar isconveniently formed of a heat conductive material such as metal and ispreferably formed of aluminum inasmuch as it can be inexpensively andreadily extruded with. the linearly extending holes 37 and 3S, and theslots 41, 42, 43 and 44 being formed in one extrusion pass.

The heating elements 40 are inserted into the holes, and a force is thenapplied to the plate 36 to collapse the slot and thereby draw or pressthe surface of the holes firmly, and in heat conductive relationship,against the outer surface of the heating element 40.

' FIGURE 8 illustrates a preferred arrangement for collapsing the slots41 and 42, by applying a localized pressure. A shaped roller 45 isforced against the top surface of the plate 36 and has ridges 46 and 47at its 'side spaced to correspond with the positions of the slots 41 and42. A supporting roller 48 backs the plate. These rollers 45 and asarerolled along the plate and the pressure will result in the surfacesof the slots being' forced together to close the slots thereby drawingthe hole 37 to a smaller diameter. As will be seen, the forces forcollapsing the slots may be applied by other means such as shapedpresses. Also, either one or both of the rollers may have cylindricalsurfaces or a table support may be employed in place of the roller 48.Also, two sets of rollers may simultaneously operate on both of theholes 37 and 38 to simultaneouslylock in both sides of the heatingelement 46 In the arrangement of FIGURE 9, a plate or bar 56) s isformed from two half slabs or bars 51 and 52. Each is of identicalconstruction and can be formed by extruding a length having the desiredshape and cutting the length into sections.

Each of the slabs has a longitudinally extending channel, as illustratedat 53 and 54 for the slab 52, and as illustrated at 55 and 56 for theslab 51. These channels are of the deformation.

exact diameter as the sides of the heating element 59 positionedtherein. Thus when the slabs 5i and 52 are pressed together, firm heatconductive engagement will occur between the inner surfaces of thechannels and the outer surface of the heating element 5?. The slabs areprovided with holes 53, and are drawn together such as by bolts orrivets 57 passing through the holes. With the channels in the slabsbeing of the size of the heating elements, when the slabs are drawntogether intimate contact must occur, and if desired the. channels canbe slightly smaller than the tubular heating element 59 so that acompressive engagement actually occurs.

The end of the lower slab is recessed, as shown at all for the slab 52in FIGURE 10. The other end of the assembly is grooved or slotted andwhen assembled a plug is positioned in the slot which will be formedbetween the slabs substantially as illustrated in connection with thearrangement of FIGURE 1.

In the arrangement illustrated in FIGURE ll, a heater bar 65 is formedof an upper slab 66 and a lower slab 67. The slabs are each providedwith longitudinal grooves of substantially the diameter of a tubularheating element '76 which fits into the grooves, and when the slabs areassembled the grooves provide longitudinally extending holes and 69 inthe bar 65.

The slabs are uniquely held together by dovetail joints formed with maleportions 71 and female portions 72. These dovetail joints provide eachof the slabs with upwardly and downwardly facing surfaces as indicatedby the angular surfaces 73 and 74. While dovetail interlocking jointsare preferred, other shapes may be employed which will interlock. Theslabs 66 and 67 may first be assembled and then the tubular heatingelements in- .plug having the structural arrangement illustrated inconnection with the bar of FIGURE 1.

of the lower slab is recessed as shown at 77. To complete the assemblyafter the tubular heating elements are in place, vertical forces areapplied to press the slabs together and a force sufficient to exceed theyield point of the metal of the slabs is used for permanent The otherend tact is achieved.

Thus it will be seen that I have provided an improved electrical heaterwhich meets the objectives, advantages and features above set forth. Amethod of making the heater is provided which avoids expensive anddisadvantageous methods heretofore available, but obtains a structurewhich provides tubular heating elements embedded in supporting plateswith intimate heat transfer contact between the elements and plates.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, out coversall modifications,

changes and alternative constructions and methods'falling' anelectrically insulative material surrounding the resistor within thetube,

an elongated one-piece retainer bar for the tube having a pair of linearelongated axially extending holes therethrough for containing the sidesof the tube,

said bar having a recess at one end opening linearly from the bar andcontaining the base of said tube,

and a close fitting heat conducting plug in said recess having anaxially facing concave recess providing a surface for being insurface-to-surface engagement with the tube to be in heat conductiverelationship with the base of said tube.

2. An electric heater comprising in combination,

an elongated resistor,

a thermally conductive tube enclosing the resistor and formed withlinear sides and a lateral base connecting the sides,

an electrically insulative material surrounding the resistor Within thetube,

an elongated one-piece'retainer bar for the tube having laterally spacedaxially extending parallel holes extending therethrough containing thesides of the tube,

said bar having an axially opening insertion slot substantially theheight of said holes and ex tending laterally across the end of the barand containing the base of the tube,

and a close fitting heat conducting plug in said recess having anaxially facing concave recess providing a surface for being insurface-to-surface engagement With the tube to be in heat conductiverelationship with the base of the tube.

3. An electric heater comprising in combination,

an elongated tubular electrical heating member with an insulatedresistor therein formed with sides and a joining base,

a heat conductive one-piece retainer bar having axially extendinglaterally spaced holes containing the sides of the member,

said bar having an axially facing end opening insertion slot at one endcontaining the base,

said one-piece bar having a portion removed at the other end extendinglaterally across the bar and exposing said holes with the ends of themember turned outwardly relative to the axis of the bar for connectionto terminals,

and a close fitting plug in said slot having an axially facing concaverecess providing a surface for being in surface-to-surface engagementwith the tube to be in heat conductive engagement with the base of saidmember.

4. An electric heater comprising in combination,

first and second elongated tubular electrical heating members withinsulated resistors therein formed with sides and a joining base,

first and second heat conductive retainer bars having laterally spacedaxially extending holes containing the sides of the members,

each of said bars having an end axially opening insertion slot at oneend containing the base of the member,

and close fitting plugs in the slots having an axially facing concaverecess providing a surface for being in surface-to-surface engagementwith the tube to be in heat conductive engagement with the base of saidmember,

6 said bars positioned to extend linearly in end-toend relationship withsaid plugs in abutting, heat conductive engagement.

5. An electric heater comprising in combination,

an elongated tubular electrical heating member with an insulatedresistor therein,

a heat conductive retainer bar having an elongated hole therein forreceiving said member,

and means defining a recess projecting radially from said hole withmaterial on each side of said recess moved together by deformation ofthe material of the bar to reduce the circumference of the hole so thatthe material of the bar which surrounds the hole is in close heatconductive engagement with the memher.

6. An electric heater comprising in combination,

an elongated tubular electrical heating member with an insulatedresistor therein,

a heat conductive metal retainer bar having laterally extending upperand lower planar surfaces and having a linearly extending hole thereinfor receiving said member,

and means defining radial laterally extending recesses in each side ofthe hole with the material on each side of said recess moved togetherand deformed to reduce the circumference of the hole with the materialof the bar which surrounds the hole being in close heat conductiveengagement with the member.

7. An electric heater comprising in combination,

an elongated tubular electrical heating member with an insulatedresistor therein formed with linear sides and a U-shaped joining base,

a heat conductive retainer bar having axially extending laterally spacedholes containing the sides of the member,

said bar having an axially facing end opening insertion slot at one endcontaining the base of the member,

a close fitting plug in said slot having an axially facing concaverecess providing a surface for being in surface-to-surface engagementwith the tube to be in heat conductive engagement with the base of saidmember,

and means defining radial slots extending laterally on both sides ofeach of the holes with the material at the sides of the slots movedtogether and deformed so that the material surrounding the holes is inheat conductive reiationship with the sides of the member.

References Cited by the Examiner UNiTED STATES PATENTS 1,828,635 10/31Abbott 219-538 X 2,042,203 5/36 Backer 219-457 2,543,970 3/51 Horsfallet a1 29-15563 2,591,442 4/52 Lucy-Hulhert et a1. 29-15564 2,725,45711/55 Norton 219-525 2,875,312 2/59 Norton 219-535 2,949,875 8/ 60 Adams29-1573 2,987,300 6/61 Greene 165-169 2,992,314 7/61 Drugmand et al219-535 3,031,739 5/62 Boggs 29-15563 3,069,526 12/62 Bremer et al219-457 3,110,795 11/63 Bremer 219-457 3,114,823 12/63 Millward 338-230X RICHARD M. WOOD, Primary Examiner.

1. AN ELECTRIC HEATER COMPRISING IN COMBINATION, AN ELONGATED RESISTOR,A THERMALLY CONDUCTIVE TUBE ENCLOSING THE RESISTOR AND FORMED WITHLINEAR SIDES ANDA LATERAL BASE CONNECTING THE SIDES, AN ELECTRICALLYINSULATIVE MATERIAL SURROUNDING THE ESISTOR WITHIN THE TUBE, ANELONGATED ONE-PIECE RETAINER BAR FOR THE TUBE HAVING A PAIR OF LINEARELONGATED AXIALLY EXTENDING HOLES THERETHROUGH FOR CONTAINING THE SIDESOF THE TUBE, SAID BAR HAVING A RECESS AT ONE END OPAENING LINEARLY FROMTHE BAR AND CONTAINING THE BASE OF SAID TUBE, AND A CLOSE FITTING HEATCONDUCTING PLUG IN SAID RECESS HAVING AN AXIALLY FACING CONCAVE RECESSPROVIDING A SURFACE FOR BEING IN SURFACE-TO-SURFACE ENGAGEMENT WITH THETUBE TO BE IN HEAT CONDUCTIVE RELATIONSHIP WITH THE BASE OF SAID TUBE.